1. Field of the Invention
The present invention relates to a scanning method for an image input system, and more particularly to a batch scanning method for an image scanner.
2. Description of the Prior Art
An image input device, like an image scanner, becomes a convenient and necessary tool in our everyday life. The scanner turns more powerful as central processing unit gets faster and memory device has more capacity. However, there exists a bottleneck in connection with time waste as a step motor drives the lamp and the charge-coupled device (CCD) back and forth when scanning multiple image sub-areas. Furthermore, while the lamp and the CCD are moving to home position after scanning any image subarea, tedious and time-consuming calibration step usually has to be performed.
FIG. 1 shows the flow diagram of a traditional method, typically called single scanning method. Initially in step 11, a color mode, a gray mode or a lineart (or called bi-level black-and-white) mode is chosen according to the attribute of an image area.
Then a calibration is performed to compensate the photo response non-uniformity of the light source, the charge-coupled device and the lens of the scanner. Thereafter, the image area is scanned (step 12), and then the lamp and the charge-coupled device are driven (in step 13) to home position, i.e., the topmost position of the whole image to be scanned, accomplishing a single scan cycle (step 14).
FIG. 2A shows the flow diagram of another conventional method, typically called multiple scanning method. FIG. 2B shows an example of scanning three image sub-areas designated as job 1, job 2, and job 3. Before processing job 1, first calibration task, step 201, is performed wherein color mode, gray mode or lineart (or bi-level black-and-white) mode is chosen according to the attribute of this sub-area or according to a received command from a user. The lamp and the CCD are driven from home position 20 to the top position 22 of the job 1, and are then driven to home position 20, step 203, after scanning, step 202, job 1's area. Next, second calibration, step 201, is practiced and job 2's area is scanned in the same manner as job 1. While there is still another job to be processed, the "YES" branch is selected in step 204, and the calibration step 201, scanning step 202 and the moving of the lamp and the CCD in step 203 are repeated. On the other hand, end of scanning is reached, step 205.
There are some disadvantages associated with the conventional method described above: (1) the repeated calibration steps for an image sub-area take a lot of time and will reduce the performance of the scanner; (2) the moving back and forth of the lamp and the CCD is time-consuming due to its mechanical driving source, for example a step motor.
According to the aforementioned drawbacks, a software method for processing multiple image areas has been devised. This software scanning method works in a way similar to the flow of FIG. 1. However, the whole image which includes all image sub-areas are scanned at once, and are then stored in memory. Thereafter, a software method is used to pick out every sub-area. The most disadvantage for this method is its use of memory more than two times the memory of any other conventional method.